I also think it is the age, having teenagers at home - and dealing with my middle school students - between, soccer, orthodontists and who knows what else - sometimes the parents just say no - too much else going on. I know we missed an opening of my son's photo club last week, while I was in NYC, because my husband had his hands full managing our household.
I am preparing for an end of year art show -I try (as always) to get something from EVERYONE into the show - I expect some very excited Kindergarten parents, and I will be thrilled if any of the middle schoolers (who are now merrily finishing their print making!) even show up!